A solenoid valve, which is known, for example, from German Patent Application No. DE 196 50 865, is used for controlling the fuel pressure in the control pressure chamber of a fuel injector, for example, of an injector of a common-rail injection system. In such injection valves, the fuel pressure in the control pressure chamber controls the movement of a valve plunger with which an injection orifice of the injection valve is opened or closed. The known solenoid valve features an electromagnet located in a housing part, a movable armature and a control-valve member which is moved together with the armature and acted upon in the closing direction by a closing spring. The control-valve member cooperates with a valve seat of the solenoid valve, thereby controlling the fuel discharge from the control pressure chamber.
A known disadvantage of the solenoid valves consists in the so-called armature bounce. When the magnet is deenergized, the closing spring of the solenoid valve accelerates the armature and, with it, the control-valve member toward the valve seat in order to close a fuel discharge passage from the control pressure chamber. The impact of the control valve member on the valve seat causes disadvantageous oscillations and/or bouncing of the control-valve member at the valve seat, which has a detrimental effect on the control of the injection process. For this reason, the solenoid valve known from German Patent Application No. DE 196 50 865 has an armature that is designed in two parts and includes an armature pin and an armature plate slidably supported on the armature pin, so that, when the valve control member strikes the valve seat, the armature plate continues its movement against the elastic force of a return spring. Subsequently, the return spring returns the armature plate to its defined original position at a stop secured to the armature pin. In this way, the armature plate is pulled up at an always identical, predefined distance when the electromagnet is reenergized.
While the effectively decelerated mass and, thus, the kinetic energy of the armature striking the valve seat, which causes the bouncing, are indeed reduced by the two-piece design of the armature with the restoring spring, the armature plate, upon which the spring force of the restoring spring acts, may oscillate on the armature pin in a disadvantageous manner once the solenoid valve is closed. During the post-oscillation process, the armature plate may strike the stop secured to the armature pin, thereby briefly opening the solenoid valve. This brief opening does not cause a significant pressure drop in the control-pressure chamber of the fuel injector and, thus, an unintended injection. However, the activation of the electromagnet for the next injection may not be initiated during this brief phase since this would affect the fuel quantity injected into the combustion chamber of the internal combustion chamber in an undefined manner, and cause serious deviations in the injection quantity. Therefore, a defined injection quantity will only be achieved again in a reliable manner once the armature plate has stopped oscillating. Restricting the duration of the post-oscillation process is of great importance, especially for representing short time intervals between, for instance, a pre-injection and a main-injection. For this reason, known solenoid valves use a fixed overtravel stop which restricts the maximum overtravel distance by which the armature plate may move on the armature pin subsequent to the control-valve member striking the valve seat. However, while this measure may reduce the post-oscillations of the armature plate, it cannot stop them.